Like many other allergies to fresh fruits and vegetables, apricot allergy can take two different forms. In the North of Europe, a milder form of apricot allergy is associated to birch-pollen allergy due to the similarity between a protein in birch that causes birch-pollen allergy, and an apricot protein. This is called the birch-fruit syndrome with symptoms confined largely to the mouth, causing a condition called “oral allergy syndrome” (OAS). The molecule, known as an allergen, involved in this kind of allergy does not survive cooking. Therefore, people who react to this allergen can tolerate cooked apricot. Individuals with apricot allergy might develop adverse reactions to other fruits including apple, pear, cherry, nuts such as hazelnut, or vegetables such as celeriac (celery tuber) and carrot.

In Mediterranean countries, people with apricot allergy do not have birch-pollen allergy. Instead they often have allergy to peach. These individuals develop adverse reactions to apricot because of the similarity between the allergens in peach and apricot. Symptoms are more severe including generalised urticaria, abdominal pain, vomiting and life-threatening symptoms, sometimes in addition to the OAS. The allergen that causes this kind of allergy is tough and the allergenicity survives in processed foods such as juices and jams. As a result, individuals with this kind of allergy cannot eat even cooked fruits. Individuals with apricot allergy also tend to develop adverse reactions to other fruits including peach, apple, cherry, plum, and nuts (such as hazelnut and walnut).

Pastorello et al. (1994) [156] and Pastorello et al. (2000) [150] used histamine dihydrochloride (10 mg/mL) as a positive control, and the glycerol-containing diluent of the prick solution as a negative control. A wheal graded at least 2+was regarded as positive.

Skin prick tests (SPTs) were carried out by the prick-prick technique. Histamine (10 mg/mL) and saline solution were used as positive and negative controls repectively. A positive SPT result was defined as a mean (average of orthogonal to largest diameter) wheal of 3 mm or greater (after subtracting the diameter of the wheal induced by the diluent control). (Rodriguez et al. 2000) [491]

Immunoblotting

Immunoblotting separation:

The extracts were separated in a discontinuous buffer system in an SDS-polyacrylamide gradient gel with a 6% stacking gel and a 7.5% to 20% separation gradient. Samples were boiled and reduced with beta-mercaptoethanol (Pastorello et al. 1994) [156], (Pastorello et al. 2000) [150]

Dose response:Patients chewed the fruit for 1 minute and then spat it out. If no symptoms appeared within 15 minutes, the challenge was repeated with increasing amounts from 4 mg up to 64 g. Patients were asked not to spit out the last two doses but to swallow the fruit instead. (Pastorello et al. 1994) [156], (Pastorello et al. 2000) [150]

Nature of main cross-reacting proteins:As a consequence of the homologies found between PR10 proteins in birch (Bet v 1), apple (Mal d 1), apricot (Pru ar 1), hazelnut (Cor a 1) and other vegetable sources, Vieths et al. (2002) [587] suggested that Pru ar 1 is involved in IgE cross-reactive allergies. In most cases Bet v 1 seems to be the sensitizing agent.

Allergen properties & biological function:This allergen is likely to be a pathogenesis-related protein and may have a role in plant protection against insect pests and microbial pathogens. However its precise function is not known.

Not known but likely to be thermostable and resistant to proteases as other members of the nsLTP family (Asero et al. 2000) [10]

Nature of main cross-reacting proteins:

IgE to Pru ar 3 cross-reacts with LTP's from other Prunoideae (eg. peach). IgE binding to nsLTP from some pollens has been implicated (Garcia-Selles et al., 2002 [594]; Pastorello et al., 2000) [150] but the relationship between allergy to pollen and fruit nsLTPs has not been clearly defined

Allergen properties & biological function:Pru ar 3 has been identified as a nonspecific lipid transfer protein (ns LTP). Plant ns LTPs are thought to be involved in transport of fatty acids both intracellular and extracellularly and of cutin monomers to the cuticular layer of leaves and fruits. There is an expandable cavity between the four alpha-helices which can bind one or two lipids. nsLTPs have also been reported to act as plant defense proteins against bacterial and fungal infections and form the PR14 family of pathogenesis related proteins. (Lindorff-Larsen et al. 2001 [903]).